Author: Aaron Beckendorf

101 Articles

Liberating AirPods With Bluetooth Spoofing

December 12, 2025 by 18 Comments

Apple’s AirPods can pair with their competitors’ devices and work as basic Bluetooth earbuds, but to no one’s surprise most of their really interesting features are reserved for Apple devices. What is surprising, though, is that simple Bluetooth device ID spoofing unlocks these features, a fact which [Kavish Devar] took advantage of to write LibrePods, an AirPods controller app for Android and Linux.

In particular, LibrePods lets you control noise reduction modes, use ear detection to pause and unpause audio, detect head gestures, reduce volume when the AirPods detect you’re speaking, work as configurable hearing aids, connect to two devices simultaneously, and configure a few other settings. The app needs an audiogram to let them work as hearing aids, and you’ll need an existing audiogram – creating an audiogram requires too much precision. Of particular interest to hackers, the app has a debug mode to send raw Bluetooth packets to the AirPods. Unfortunately, a bug in the Android Bluetooth stack means that LibrePods requires root on most devices.

This isn’t the first time we’ve seen a hack enable hearing aid functionality without official Apple approval. However, while we have some people alter the hardware, AirPorts can’t really be called hacker- or repair-friendly.

Thanks to [spiralbrain] for the tip!

A man's hands are holding an assembly of 3D-printed parts. There is a white backplate, with a yellow circular piece running through the middle. The yellow piece is surrounded by metal rods. Another blue shaft runs through the left side of the assembly. A rougly-diamond shaped plate encompasses both of these shafts.

Designing A Simpler Cycloidal Drive

December 11, 2025 by 1 Comment

Cycloidal drives have an entrancing motion, as well as a few other advantages – high torque and efficiency, low backlash, and compactness among them. However, much as [Sergei Mishin] likes them, it can be difficult to 3D-print high-torque drives, and it’s sometimes inconvenient to have the input and output shafts in-line. When, therefore, he came across a video of an industrial three-ring reducing drive, which works on a similar principle, he naturally designed his own 3D-printable drive.

The main issue with 3D-printing a normal cycloidal drive is with the eccentrically-mounted cycloidal plate, since the pins which run through its holes need bearings to keep them from quickly wearing out the plastic plate at high torque. This puts some unfortunate constraints on the size of the drive. A three-ring drive also uses an eccentric drive shaft to cause cycloidal plates to oscillate around a set of pins, but the input and output shafts are offset so that the plates encompass both the pins and the eccentric driveshaft. This simplifies construction significantly, and also makes it possible to add more than one input or output shaft.

As the name indicates, these drives use three plates 120 degrees out of phase with each other; [Sergei] tried a design with only two plates 180 degrees out of phase, but since there was a point at which the plates could rotate just as easily in either direction, it jammed easily. Unlike standard cycloidal gears, these plates use epicycloidal rather than hypocycloidal profiles, since they move around the outside of the pins. [Sergei] helpfully wrote a Python script that can generate profiles, animate them, and export to DXF. The final performance of these drives will depend on their design parameters and printing material, but [Sergei] tested a 20:1 drive and reached a respectable 9.8 Newton-meters before it started skipping.

Even without this design’s advantages, it’s still possible to 3D-print a cycloidal drive, its cousin the harmonic drive, or even more exotic drive configurations. Continue reading “Designing A Simpler Cycloidal Drive” →

A circular 3D-printed board is shown, with a roughly star-shaped pattern of white LEDs glowing through the surface. Yellow and green LEDs are also visible through the surface at a few points.

Adding Electronics To A Classic Game

December 5, 2025 by No comments

Like many classic board games, Ludo offers its players numerous opportunities to inflict frustration on other players. Despite this, [Viktor Takacs] apparently enjoys it, which motivated him to build a thoroughly modernized, LED-based, WiFi-enabled game board for it (GitHub repository).

The new game board is built inside a stylish 3D-printed enclosure with a thin white front face, under which the 115 LEDs sit. Seven LEDs in the center represent a die, and the rest mark out the track around the board and each user’s home row. Up to six people can play on the board, and different colors of the LEDs along the track represent their tokens’ positions. To prevent light leaks, a black plastic barrier surrounds each LED. Each player has one button to control their pieces, with a combination of long and short presses serving to select one of the possible actions.

The electronics themselves are mounted on seven circuit boards, which were divided into sections to reduce their size and therefore their manufacturing cost. For component placement reasons, [Viktor] used a barrel connector instead of USB, but for more general compatibility also created an adapter from USB-C to a barrel plug. The board is controlled by an ESP32-S3, which hosts a server that can be used to set game rules, configure player colors, save and load games, and view statistics for the game (who rolled the most sixes, who sent other players home most often, etc.).

If you prefer your games a bit more complex, we’ve also seen electronics added to Settlers of Catan. On a rather larger scale, there is also this LED-based board game which invites humans onto the board itself. Continue reading “Adding Electronics To A Classic Game” →

A mirrorless camera is mounted on a stand, facing downwards toward a rotating microscope stage made of wood. A pair of wires come down from the stage, and a man's hand is pointing to the stage.

Building A Microscope Without Lenses

December 4, 2025 by 7 Comments

It’s relatively easy to understand how optical microscopes work at low magnifications: one lens magnifies an image, the next magnifies the already-magnified image, and so on until it reaches the eye or sensor. At high magnifications, however, that model starts to fail when the feature size of the specimen nears the optical system’s diffraction limit. In a recent video, [xoreaxeax] built a simple microscope, then designed another microscope to overcome the diffraction limit without lenses or mirrors (the video is in German, but with automatic English subtitles).

The first part of the video goes over how lenses work and how they can be combined to magnify images. The first microscope was made out of camera lenses, and could resolve onion cells. The shorter the focal length of the objective lens, the stronger the magnification is, and a spherical lens gives the shortest focal length. [xoreaxeax] therefore made one by melting a bit of soda-lime glass with a torch. The picture it gave was indistinct, but highly magnified. Continue reading “Building A Microscope Without Lenses” →

A 3D-printed assembly standing on short legs is visible. A portion extends upward with the word "Nord" sunk into it. Cables extend from one side of the upright portion, and a side view of a circuit board is visible at the front of the assembly.

Measuring Earth’s Rotation With Two Gyroscopes

November 23, 2025 by 43 Comments

We’ve probably all had a few conversations with people who hold eccentric scientific ideas, and most of the time they yield nothing more than frustration and perhaps a headache. In [Bertrand Selva]’s case, however, a conversation with a flat-earth believer yielded a device that uses a pair of gyroscopes to detect earth’s rotation, demonstrating that rotation exists without the bulkiness of a Foucalt pendulum.

[Bertrand] built his apparatus around a pair of BMI160 MEMS gyroscopes, which have a least significant bit for angular velocity corresponding to 0.0038 degrees per second, while the earth rotates at 0.00416 degrees per second. To extract such a small signal from all the noise in the measurements, the device makes measurements with the sensors in four different positions to detect and eliminate the bias of the sensors and the influence of the gravitational field. Before running a test, [Bertrand] oriented the sensors toward true north, then had a stepper motor cycle the sensors through the four positions, while a Raspberry Pi Pico records 128 measurements at each position. It might run the cycle as many as 200 times, with error tending to decrease as the number of cycles increases.

A Kalman filter processes the raw data and extracts the signal, which came within two percent of the true rotational velocity. [Bertrand] found that the accuracy was strongly dependent on how well the system was aligned to true north. Indeed, the alignment effect was so strong that he could use it as a compass.

In the end, the system didn’t convince [Bertrand]’s neighbor, but it’s an impressive demonstration nonetheless. This system is a bit simpler, but it’s also possible to measure the earth’s rotation using a PlayStation. For higher precision, check out how the standards organizations manage these measurements.

A circular metal vessel is shown, with a symmetrical rotor of four vanes standing inside. At the bottom of the vessel are four loudspeakers.

Building An Acoustic Radiometer

November 22, 2025 by 12 Comments

A Crookes radiometer, despite what many explanations claim, does not work because of radiation pressure. When light strikes the vanes inside the near-vacuum chamber, it heats the vanes, which then impart some extra energy to gas molecules bouncing off of them, causing the vanes to be pushed in the opposite direction. On the other hand, however, it is possible to build a radiometer that spins because of radiation pressure differences, but it’s easier to use acoustic radiation than light.

[Ben Krasnow] built two sets of vanes out of laser-cut aluminium with sound-absorbing foam attached to one side, and mounted the vanes around a jewel bearing taken from an analog voltmeter. He positioned the rotor above four speakers in an acoustically well-sealed chamber, then played 130-decibel white noise on the speakers. The aluminium side of the vanes, which reflected more sound, experienced more pressure than the foam side, causing them to spin. [Ben] tested both sets of vanes, which had the foam mounted on opposite sides, and they spun in opposite directions, which suggests that the pressure difference really was causing them to spin, and not some acoustic streaming effect.

The process of creating such loud sounds burned out a number of speakers, so to prevent this, [Ben] monitored the temperature of a speaker coil at varying amounts of power. He realized that the resistance of the coil increased as it heated up, so by measuring its resistance, he could calculate the coil’s temperature and keep it from getting too hot. [Ben] also tested the radiometer’s performance when the chamber contained other gasses, including hydrogen, helium, carbon dioxide, and sulfur hexafluoride, but none worked as well as air did. It’s a bit counterintuitive that none of these widely-varying gasses worked better than air did, but it makes sense when one considers that speakers are designed to efficiently transfer energy to air.

It’s far from an efficient way to convert electrical power into motion, but we’ve also seen several engines powered by acoustic resonance. If you’d like to hear more about the original Crookes radiometers, [Ben]’s also explained those before.

A microscope objective is sitting on a spool of solder in a metal tin, in front of a circuit board which has wires running away from it.

Watching Radioactive Decay With A Homemade Spinthariscope

November 17, 2025 by 2 Comments

Among the many science toys that have fallen out of fashion since we started getting nervous around things like mercury, chlorinated hydrocarbons, and radiation is the spinthariscope, which let people watch the flashes of light on a phosphor screen as a radioactive material decayed behind it. In fact, they hardly expose their viewers to any radiation, which makes [stoppi]’s homemade spinthariscope much safer than it might first seem.

[Stoppi] built the spinthariscope out of the eyepiece of a telescope, a silver-doped zinc sulfide phosphor screen, and the americium-241 capsule from a smoke detector. A bit of epoxy holds the phosphor screen in the lens’s focal plane, and the americium capsule is mounted on a light filter and screwed onto the eyepiece. Since americium is mainly an alpha emitter, almost all of the radiation is contained within the device.

After sitting in a dark room for a few minutes to let one’s eyes adjust, it’s possible to see small flashes of light as alpha particles hit the phosphor screen. The flashes were too faint for a smartphone camera to pick up, so [stoppi] mounted it in a light-tight metal box with a photomultiplier and viewed the signal on an oscilloscope, which revealed many small pulses.

Continue reading “Watching Radioactive Decay With A Homemade Spinthariscope” →